Mesoscale Discussion 821

Issued

May 15, 2012, 6:30 PM EDT (22:30 UTC)

Expired

May 15, 2012, 8:00 PM EDT

In force

90 min

Issued by

the Storm Prediction Center

The Columbia radar (KCAE), 127 km from the middle of the area, began a volume at 22:31 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

706 
ACUS11 KWNS 152231
SWOMCD
SPC MCD 152230
NCZ000-SCZ000-GAZ000-160000-

MESOSCALE DISCUSSION 0821
NWS STORM PREDICTION CENTER NORMAN OK
0530 PM CDT TUE MAY 15 2012

AREAS AFFECTED...SC...PORTIONS OF NC...ERN GA

CONCERNING...SEVERE THUNDERSTORM WATCH 278...279...

VALID 152230Z - 160000Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH
278...279...CONTINUES.

SUMMARY...THE THREAT FOR TSTMS WITH SVR WIND GUSTS AND MARGINALLY
SVR HAIL WILL PERSIST INTO THE EVENING.

DISCUSSION...DEEP CONVECTION WILL PERSIST ACROSS SEVERE THUNDERSTORM
WATCHES 278 AND 279 INTO THE EVENING. THE THREAT WILL BE FOCUSED IN
TWO BROAD AREAS:

/1/ ACROSS THE PIEDMONT AND COASTAL PLAIN OF SC: THIS REGION IS
INVOF AND TO THE EAST OF A DIFFUSE/QUASI-STATIONARY SFC FRONT
STRETCHING FROM 25 MILES SSE OF CHARLOTTE NC TO 25 MILES SSW OF
AUGUSTA GA...WITH THE FRONT COINCIDING WITH THE WRN FRINGES OF
RICHER DEEP MOISTURE OVER CNTRL/ERN PARTS OF SC /PW VALUES OF
1.5-1.6 INCHES PER GPS DATA/. ASCENT ALONG THE FRONT...AND ASCENT TO
ITS EAST ALONG OUTFLOW BOUNDARIES AMIDST A MODERATELY UNSTABLE AIR
MASS...WILL FOSTER A CONTINUED THREAT FOR ROBUST/REGENERATIVE
CONVECTION INTO THE EVENING. WITH AROUND 30 KT OF DEEP SHEAR PER
COLUMBIA SC VWP DATA...MULTICELL CLUSTERS WILL BE THE MAIN
CONVECTIVE MODE...THOUGH AN TRANSIENT/WEAK SUPERCELL STRUCTURE
CANNOT BE RULED OUT...WITH ATTENDANT THREATS OF DMGG WIND GUSTS AND
MARGINALLY SVR HAIL.

/2/ ELSEWHERE: WHILE DEEP MOISTURE IS COMPARATIVELY LESS RICH...A
WELL-DEFINED...NWWD-MOVING AGGREGATE OUTFLOW/SEA BREEZE BOUNDARY
FROM HALIFAX COUNTY NC SWWD TO SCOTLAND COUNTY NC IS NOTED VIA THE
FINE LINE IN 0.5-DEGREE RALEIGH REFLECTIVITY DATA. CONVECTION WILL
LIKELY CONTINUE TO FORM ALONG OR JUST BEHIND THE BOUNDARY...POSING
MAINLY A THREAT FOR MARGINALLY SVR HAIL AS CLOUD-LAYER WINDS STEER
STORMS INTO THE RELATIVELY MORE STABLE AIR MASS EAST OF THE
BOUNDARY. ALSO...OROGRAPHIC ASCENT IS SUPPORTING CONVECTION OVER
PARTS OF THE SRN APPALACHIANS. THIS ACTIVITY MAY INTENSIFY AS IT
MOVES OVER PARTS OF THE ADJACENT PIEDMONT REGION WHERE MODERATE
INSTABILITY AMIDST MODEST MID-LEVEL FLOW MAY SUPPORT OCCASIONALLY
ORGANIZED STORM STRUCTURES WITH THREATS FOR DMGG WIND GUSTS AND
MARGINALLY SVR HAIL.

..COHEN.. 05/15/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...MHX...RAH...ILM...RNK...CHS...CAE...GSP...JAX...
FFC...

LAT...LON   31358081 31398146 31938215 32938223 33818280 34518347
            35168309 36048189 36168074 36317975 36357935 36367820
            36277773 35907733 35667750 35117805 34727806 34657759
            34407732 33927748 33437824 32947901 31858011 31358081

Mesoscale Discussions in North Carolina, 2012Mesoscale Discussions in South Carolina, 2012Mesoscale Discussions in Georgia, 2012Every mesoscale discussion in 2012

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.